Kinetic equations for Stark line shapes

The BBGKY formalism is revisited in the framework of plasma spectroscopy. We address the issue of Stark line shape modeling by using kinetic transport equations. In the most simplified treatment of these equations, triple correlations between an emitter and the perturbing charged particles are neglected and a collisional description of Stark effect is obtained. Here we relax this assumption and retain triple correlations using a generalization of the Kirkwood truncature hypothesis to quantum operator. An application to hydrogen lines is done in the context of plasma diagnostic, and indicates that the neglect of triple correlations can lead to a significant overestimate of the line width.Comment: 13 pages, 1 figur

Philippians 2:6-11: Pre-Existence or Second Adam Christology? A Comparison of the Exegeses of Three Modern Scholars with that of St. John Chrysostom

At least two major Christologies have been found in Philippians 2:6-11, which is otherwise known as the Philippians hymn. One group of biblical scholars argues for a Christology of a pre-existent, divine being who had full equality with God from eternity. This is often referred to as pre-existence Christology. Under this Christology, the pre-existent Christ did not need to grasp at full equality with God because he already had it. Instead, he chose to empty himself, becoming a human being (a slave ) and to humble himself by being obedient to death. After his death and resurrection, God exalted him back to the status that he had in his pre-existence: full equality with God. A second group of biblical scholars argues that in Phil 2:6-11 Paul (or whoever authored the hymn) was not describing a pre-existent, divine being but rather the earthly Jesus of Nazareth. These scholars generally interpret the periscope as exhibiting a Second Adam Christology. According to this Christology, the earthly Jesus described in the hymn did not have equality with God. Christ made a choice - unlike the Adam of Genesis - not to grasp at equality with God, but to be obedient to God by accepting death

Essential Concepts for the First Year of Study for BSc Mathematics

To inform discussion about content for the first year of undergraduate mathematics, a study was completed which reviewed: the A-level Mathematics specification; published literature on the transition from A-level to university mathematics; the second and third year curricula of modules at three English universities with different foci. This aimed to investigate what students might reasonably be expected to have covered when they arrive at university, what happens in practice at the transition to university, and the role of the first year as preparation for later study. Content suggestions focus on calculus, linear algebra and analysis as core topics. There is also evidence of the need to focus on students' understanding of where formulae and solutions originated as well as their ability to produce pieces of academic and mathematical writing. Findings also include suggestion that what happens in the first year, while similar between institutions, does depend on the overall focus of the degree programme

Early Years Professional Status Impact Study – Final Report: Achieving outcomes in Essex

This three year study aimed to explore the impact of Early Years Professional Status on outcomes for children. The graduate leader status is part of the professionalisation of the Early Years sector and the research occurred between 2010 and 2013. Data was collected using questionnaires, interviews and focus groups with members of the early years workforce and documentary analysis of Ofsted reports. Findings demonstrate that the graduate leader is having an important impact on improving outcomes for children against the five areas of being healthy; staying safe; enjoying and achieving; making a positive contribution and achieving economic wellbeing. This is an important study of the value of the graduate leader in the context of changing early years policy

Influence of correlated collisions on Stark-broadened lines in plasmas

International audienceAn investigation of spectral line broadening in plasmas is carried out within a kinetic-theory approach, based on the Bogoliubov-Born-Green-Kirkwood-Yvon (BBGKY) hierarchy. The model employs a resummation procedure to account for correlated emitter-perturber collisions. Applications to hydrogen lines indicate that such collisions strongly affect the width and the shape in the core region. This argument is supported by comparisons to numerical simulations. It is also shown that the usual collision operator models, based on a binary description of emitter-perturber collisions, can be extremely inaccurate. The present model, in a better agreement with numerical simulations, is suggested as an extension suitable for the design of fast and accurate numerical routines for plasma diagnostics

Divergence of the Stark collision operator at large impact parameters in plasma spectroscopy models

International audienceThe divergence that occurs at large impact parameters in Stark collision operators is examined for low-density hydrogen plasmas. In a previous work [Rosato, Capes, and Stamm, Phys. Rev. E \textbf{86}, 046407 (2012)], we showed that the correlations between a radiating atom and the charged particles surrounding it affect the mean evolution of the atom, resulting in a mitigation of the Stark broadening near the line center. In this work, we examine the physical mechanism underlying this mitigation with an approach inspired from the standard semi-classical impact model. Our approach accounts for the atom-perturber correlations in a simple fashion, through a cut-off at large impact parameters, and embraces the impact model in the weakly coupled plasma limit. Comparisons with numerical simulations are performed and indicate a good agreement

Ideal Coulomb plasma approximation in line shape models: problematic issues

International audienceIn weakly coupled plasmas, it is common to describe the microfield using a Debye model. We examine here an “artificial” ideal one-component plasma with an infinite Debye length, which has been used for the test of line shape codes. We show that the infinite Debye length assumption can lead to a misinterpretation of numerical simulations results, in particular regarding the convergence of calculations. Our discussion is done within an analytical collision operator model developed for hydrogen line shapes in near-impact regimes. When properly employed, this model can serve as a reference for testing the convergence of simulations

Function and biotechnology of extremophilic enzymes in low water activity

Enzymes from extremophilic microorganisms usually catalyze chemical reactions in non-standard conditions. Such conditions promote aggregation, precipitation, and denaturation, reducing the activity of most non-extremophilic enzymes, frequently due to the absence of sufficient hydration. Some extremophilic enzymes maintain a tight hydration shell and remain active in solution even when liquid water is limiting, e.g. in the presence of high ionic concentrations, or at cold temperature when water is close to the freezing point. Extremophilic enzymes are able to compete for hydration via alterations especially to their surface through greater surface charges and increased molecular motion. These properties have enabled some extremophilic enzymes to function in the presence of non-aqueous organic solvents, with potential for design of useful catalysts. In this review, we summarize the current state of knowledge of extremophilic enzymes functioning in high salinity and cold temperatures, focusing on their strategy for function at low water activity. We discuss how the understanding of extremophilic enzyme function is leading to the design of a new generation of enzyme catalysts and their applications to biotechnology